It is known to make various types of chopped or continuous glass fiber mats, with or without synthetic polymer fibers or other fibers. Woven or nonwoven fiber mats comprising glass fibers bonded together thermosetting resins, like urea formaldehyde, melamine formaldehyde resin or phenolic resole resins, acrylic resins, modified with one or more plasticizers or plain, as disclosed in U.S. Pat. No. 5,840,413, and to use various thermoplastic resins including polyvinyl acetate, polyvinyl alcohol, styrene-butadiene-rubber, styrene-butadiene-stryrene, styrene acrylic copolymers, polyvinyl chloride, flame retardant acrylics or brominated monomer additions to acrylic, usually applied as a latex. It is also known to use such mats in various roofing and foam facer applications, and to use some of these mats as facers for making cementitious boards like gypsum wallboard or backer board. In the latter application, the fibers in the mats are preferably bound with acrylic, phenolic or polyvinyl chloride based binders, but latex binders including ethylene-vinyl-chloride, polyvinyl acetate, ethylene vinyl versatate, polyvinylidene chloride, PVOH, polyester, SBR, urethane, silicone, melamines, ethylene-vinyl-acetate, metallic resonates, wax, asphalt, acrylic resins, styrene acrylate copolymers, aromatic isocyanates and diisocynates, organohydrogenpolysiloxanes, epoxies, phenolics, an acidulated water-soluble copolymer comprised of methacrylic acid and dimethyldiallyammonium chloride are also mentioned. Some binder mixtures such as a 70 wt. % urea formaldehyde resin with 30 wt. % acrylic latex mixture with a carboxylated polymer addition, ethylene/vinyl acetate and vinyl acetate/vinyl versatate copolymers are also disclosed. Such mats for use with cementations materials are disclosed in U.S. Pat. Nos. 6,770,354, 6,749,720, 6,808,793, 6,931,131, 6,995,098, 7,049,251, 7,297,396, 7,354,876, and 7,429.544, and published U.S. Pat. Application Nos. 2002/0151240 A1, 2003/0129903 A1, 2003/0175478 A1, and 2005/0202742 A1.
It is also known to make nonwoven fibrous mats containing polyether imide fibers and glass fibers bonded together with a melamine formaldehyde binder, as disclosed in U.S. Pat. No. 7,250,381, for use as a facer against a fiber reinforced thermoplastic and thermoformable layer. It is also known, as disclosed in U.S. Pat. Nos. 6,875,308 and 7,285,183, to make a facer for gypsum wall board by foam coating a wet laid glass fiber mat containing a cured binder such as urea formaldehyde resin, melamine formaldehyde resin or other resin binders. It is also known to make a roofing felt by needling synthetic polymer fibers into a nonwoven glass fiber mat containing a cured melamine formaldehyde binder as disclosed in U.S. Pat. No. 7,199,065, and to make a facer mat having good hiding power comprising glass fibers, a paper coating material and any known mat binder including melamine formaldehyde, the mats for use in making products like tack board, wall board, etc., see U.S. Pat. No. 7,435,694.
It is also known to make nonwoven fiber glass mats by chopping dry strands of glass fibers bound together with a binder to form chopped strand, to collect the chopped strand on a moving conveyor in a random pattern, and to bond the chopped strand together at their crossings by dusting a dry, powdered thermoplastic binder like a polyamide, polyester or ethylene vinyl acetate on wetted chopped strands followed by drying and curing the binder, as disclosed in U.S. Pat. No. 5,565,049. While such mat products are very useful including bonding to a layer of polymeric foam to stiffen the foam, these mats do not have as high a tensile strength as desired, and as achieved with a wet laid nonwoven fiber glass mat, because the bundles or chopped strands in the mat, according to the invention of the above cited patent, do not bond together as well as the individual fibers in a typical nonwoven mat. It is also known to use bundles of chopped strands, bundles of a plurality of fibers bonded together with a thermoplastic or thermoset binder, in a wet laid nonwoven mat as disclosed in U.S. Pat. No. 4,129,674.
It is also known to make a nonwoven fiber glass mat bonded with “B” staged acrylic resin having a glass transition temperature above 45 degrees C. and to use such mats to form a laminate with a foam layer for use in automotive head liners as disclosed in U.S. Pat. No. 6,008,147, but this mat is not well suited for laminating to a polymeric fibrous web when the desired shape contains complex curvatures requiring the mat to stretch substantially during molding. Further, it is known to use an acrylic copolymer latex, such as a self cross linking acrylic copolymer of an anionic emulsifying type as one component of at least a two component binder for bonding glass fibers and particulate thermoplastic to make a glass fiber reinforced sheet that can later be hot molded into various shapes and articles, as disclosed in U.S. Pat. No. 5,393,379.
What is still needed is a fibrous mat or facer having better alkaline resistance for use in contact with alkaline cementitious materials to provide laminates having superior alkaline resistance.